Add a Dns preresolve interface in //content

content/browser/loader/resource_dispatcher_host_impl.h

Index: content/browser/loader/resource_dispatcher_host_impl.h
diff --git a/content/browser/loader/resource_dispatcher_host_impl.h b/content/browser/loader/resource_dispatcher_host_impl.h
index 3d960faa85ad57391bc7d6a6eed2b724bdf6ff52..a0adbb1af1e90e72186c0febc6193c2718d69055 100644
--- a/content/browser/loader/resource_dispatcher_host_impl.h
+++ b/content/browser/loader/resource_dispatcher_host_impl.h
@@ -69,6 +69,7 @@ class NavigationURLLoaderImplCore;
 class RenderFrameHostImpl;
 class ResourceContext;
 class ResourceDispatcherHostDelegate;
+class ResourceHintsController;
 class ResourceMessageDelegate;
 class ResourceMessageFilter;
 class ResourceRequestInfoImpl;
@@ -318,6 +319,10 @@ class CONTENT_EXPORT ResourceDispatcherHostImpl
   // or experiment status. For unit tests only.
   void EnableStaleWhileRevalidateForTesting();
 
+  ResourceHintsController* resource_hints_controller() {
+    return resource_hints_controller_.get();
+  }
+
  private:
   friend class LoaderIOThreadNotifier;
   friend class ResourceDispatcherHostTest;
@@ -659,6 +664,8 @@ class CONTENT_EXPORT ResourceDispatcherHostImpl
 
   std::unique_ptr<ResourceScheduler> scheduler_;
 
+  std::unique_ptr<ResourceHintsController> resource_hints_controller_;
+
   // Allows tests to use a mock CertStore. If set, the CertStore must
   // outlive this ResourceDispatcherHostImpl.
   CertStore* cert_store_for_testing_;